1. Field of the Invention
The present invention relates to a driving mechanism of a circuit breaker to be used in an electric power line system, and especially relates to a driving mechanism having two hydraulic operation apparatuses which drive a main contact and a resistor contact of the circuit breaker.
2. Description of the Prior Art
When the voltage of an electric power system becomes higher and the conventional circuit breaker is used, for example, in 1000 kv system, it is demanded to restrain an overvoltage not only in the closing operation but also in the breaking operation of the circuit breaker for making a transmission-transformation system and/or transmission lines economical. For restraining the overvoltage in the breaking operation too, a resistor-breaking type circuit breaker, which inserts a resistor contact after breaking the main contact and breaking the resistor contact after a predetermined time period, is necessary. For such a time period of the insertion time of the resistor contact, a computer simulation of the model system revealed that a time of about 25 ms is necessary. That is, a longer time period in comparison with that of 10 ms in the resister insertion operation.
On the other hand, the circuit breaker is requested to operate faster in the breaking operation than in the closing operation for obtaining a high circuit breaking performance, generally. For satisfying such a condition, it is necessary that the resistor contact is opened in the vicinity of the final step of the breaking operation after the main contact is opened. Therefore, other special driving apparatuses are demanded for driving the main contact and the resistor contact, independently.
A conventional circuit breaker with resistor contact is shown in FIG.9 which is a sectional side view schematically showing a typical constitution of the circuit breaker. In FIG.9, insulative gas such as SF.sub.6 is filled in an inner space 201 of a tank 200. A series connection of a resistor 202 and a resistor contact 401 is connected in parallel with a main contact 1. The main contact 1 is coupled with a first differential piston 3 of a first hydraulic operation apparatus 4 via a first link mechanism 2, and the resistor contact 401 is coupled with a second differential piston 403 of a second hydraulic operation apparatus 104 via a second link mechanism 402. The first and second hydraulic operation apparatuses 4 and 104 are respectively provided outside the tank 200. The first link mechanism 2 is constituted by an insulative operation rod 2a, a link 2b, a rod end 2c, and so on. The second link mechanism 402 is also constituted by an insulative operation rod 402a, a link 402b, a rod end 402c and so on. Since the link mechanisms are well known in the art, they are schematically illustrated in the figure. As is obvious in the art, the insulative operation rods 2a and 402a are provided for slidably penetrating a shell of the tank 200 via gas-tight sealing elements from the inner space of the tank 200 to the atmosphere.
A conventional hydraulic operation apparatus, which is to be used as an actuator of the conventional driving mechanism of the circuit breaker, is described referring to FIGS. 10, 11 and 12. Such a conventional hydraulic operation apparatus is, for example, shown in Publication Gazette of Japanese Patent Application Sho 61-156613.
FIGS. 10 and 12 are sectional side views showing a constitution of the conventional first hydraulic operation apparatus. FIG. 11 shows timing charts of the operation of the conventional hydraulic operation apparatus. Since the second hydraulic operation apparatus has substantially the same constitution of the first hydraulic operation apparatus, only the explanation of the first hydraulic operation apparatus is described referring to the figures.
In FIGS. 10 and 12, a driving device 6 for driving the main contact 1 comprises a differential piston 3, a cylinder 5 and dashpot rings 24 and 74. An end 3a of the differential piston 3 is connected to the main contact 1 of the circuit breaker via a link mechanism 2. A first pressure chest 5a of the cylinder 5 which is positioned in a smaller piston area side of the differential piston 3 is connected to an accumulator 9 through a pipe line 10. A second pressure chest 5b of the cylinder 5 is positioned in a larger piston area side of the differential piston 3.
A main valve 7, which is used for controlling the driving device 6, is provided neighboring to the driving device 6. The main valve 7 consists of a main valve chest 7a, a feed valve 13 and an exhaust valve 14. The feed valve 13 comprises a compression spring 13a, a valve body 13b and a pilot chest 13c. The exhaust valve 14 also comprises a compression spring 14a, a valve body 14b and a pilot chest 14c. The pilot chest 13c is connected to the accumulator 9 through the pipe line 11. The main valve chest 7a is connected to the second pressure chest 5b of the cylinder 5 of the driving device 6. The valve bodies 13b and 14b are positioned to face to each other and coupled to move in one body.
An amplifier valve 8 comprises an amplifier valve chest 8a, a supplemental exhaust valve 19 and a supplemental feed valve 20. The supplemental exhaust valve 19 comprises a compression spring 19a, a valve body 19b and a pilot chest 19c. The supplemental feed valve 20 also comprises a compression spring 20a, a valve body 20b and a pilot chest 20c. The valve bodies 19b and 20b are positioned back to back each other and coupled to move in one body. The pilot chest 14c of the exhaust valve 14 of the main valve 7 and the amplifier valve chest 8a of the amplifier valve 8 are connected by a pipe line 16. As shown in FIG. 10, a pipe line 20d is provided on the valve body 20b, and thereby, the amplifier valve chest 8a and the pilot chest 20c is connected. Furthermore, pipe lines 12 and 51 are provided for connecting to the accumulator 9 and the amplifier valve chest 8a of the amplifier valve 8. The second pressure chest 5b of the cylinder 5 of the driving device 6 and the pilot chest 19c of the supplemental exhaust valve 19 is connected by pipe lines 71 and 77 and a restrictor 72. The second pressure chest 5b of the cylinder 5 is connected to the accumulator 9 through pipe lines 76, 11 and 10 and a restrictor 75.
A closing valve 38, which is to be used in closing operation of the circuit breaker, is configured in a manner to connected to a valve chest 38a and the accumulator 9 by pipe lines 12, 52 and 56 and a restrictor 54. Thereby, the high-pressure oil is supplied from the accumulator 9 to the closing valve 38. An opening valve 28, which is to be used in opening operation of the circuit breaker, is configured in a manner to connect to a valve chest 28a and the pilot chest 19c of the supplemental exhaust valve 19 by a pipe line 57. The valve chest 28a of the opening valve 28 is connected to a lower-pressure tank 18 through a pipe line 58. Furthermore, the lower-pressure tank 18 is connected to the exhaust valve 14 of the main valve 7 through a pipe line 17. The supplemental exhaust valve 19 is also connected to the lower-pressure tank 18 through a pipe line 22. The valve chest 38a of the closing valve 38 is also connected to the lower-pressure tank 18 through a pipe line 60.
The closing valve 38 comprises a ball-shaped valve body 29 and a compression spring 31. The opening valve 28 also comprises a ball-shaped valve 30 and a compression spring 32. The closing valve 38 is controlled by an electro-magnetic device 35 via an operation rod 33. The opening valve 28 is also controlled by another electro-magnetic device 36 via another operation rod 34. Each electro-magnetic device 35 or 36 comprises a moving core 35a or 36a and a stationary coil 35b or 36b, wherein the moving core 35a or 36a moves linearly by responding to magnetic force generated by the stationary coil 35b or 36b.
A pipe line 59 is branched from the pipe line 56. The pipe line 59 is connected to a closing operation control device 61. The closing operation control device 61 comprises a smaller piston 62 which is driven by the high-pressure oil supplied to the closing operation controlling device 61. A latch 63 is provided in the vicinity of the closing operation control device 61. The latch 63 is rotatably borne by a pivot 64 which is, for example, fixed on the cylinder 5. When the high-pressure oil is supplied to the closing operation control device 61, the piston 62 is driven to move leftward in FIG. 10, and the piston 62 pushes the back face of the latch 63. When the latch 63 has been pushed by the piston 62, the latch 63 can rotate. As shown in FIG. 12, when the latch 63 is engaged with a pin 50 which is provided on the differential piston 3, the engagement is maintained. The latch 63 has a specific shape in a manner that the latch 63 is automatically rotated in clockwise direction in FIG. 12 for releasing the engagement with the pin 50 by receiving thrust from the differential piston 3. When the pushing force of the piston 62 is removed, the latch 63 starts to rotate by the force from the differential piston 3.
The dashpot ring 74 is allowed to slightly move up and down along an inner surface of the cylinder 5. A circular groove 73 is provided on an outer periphery of the dashpot ring 74 for connecting to the pipe lines 76 and 77. When the dashpot ring 74 is pushed down by the differential piston 3, and oil-tightly seals the communication from the second pressure chest 5b of the cylinder 5, the high-pressure oil flows from the pipe line 76 to the pipe line 77 through the circular groove 73. On the other hand, when the dashpot ring 74 is not pushed down by the differential piston 3, and the pressure of the oil in the pipe lines 76 and 77 is larger than the pressure in the second pressure chest 5b of the cylinder 5, the dashpot ring 74 floats. Thereby, the second pressure chest 5b of the cylinder 5 and the pipe lines 76 and 77 are connected.
The opening operation of the contacts in the above-mentioned conventional driving mechanism of the circuit breaker is described referring to FIG. 11 which shows timing charts of the operation.
In FIG. 11, timing chart (a) shows timing of ON and OFF of excitation signal of the above-mentioned conventional electro-magnetic device 36 which is to be used for opening the contacts of the circuit breaker. Timing chart (b) shows the pressure of the oil in the pilot chest 19c of the supplemental exhaust valve 19. Timing chart (c) shows the position of the supplemental exhaust valve 19 and the supplemental feed valve 20 which move in one body. Timing chart (d) shows the pressure of the oil in the pilot chest 14c of the exhaust valve 14. Timing chart (e) shows the position of the feed valve 13 and the exhaust valve 14 which move in one body. Timing chart (f) shows the pressure of the oil in the second pressure chest 5b of the cylinder 5. Timing chart (g) shows the movement of the differential piston 3. Timing chart (h) shows the movement of the latch 63. And timing chart (i) shows the pressure of the oil in the circular groove 73.
In FIG. 10 which shows the closing state of the conventional driving mechanism of the circuit breaker, when the opening signal is inputted to the electromagnetic device 36 at the point of time a1 in the timing chart (a) in FIG. 11, the stationary core 36b is excited, and the moving core 36a moves for switching the opening valve 28 via the operation rod 34. Thereby, the ball-shaped valve body 30 is opened. As a result, the pilot chest 19c of the supplemental exhaust valve 19 of the amplifier valve 8 is connected to the lower-pressure tank 18 via the pipe lines 57 and 58. The high-pressure oil in the pilot chest 19c is exhausted to the lower-pressure tank 18 at a point of time b1 in the timing chart (b) in FIG. 11. When the high-pressure oil in the pilot chest 19c is exhausted, the valve bodies 19b and 20b start to move upward in FIG. 10. By such operation, the pipe lines 16 and 22 are connected at a point of time cl in the timing chart (c) in FIG. 11. Therefore, the pilot chest 14c of the exhaust valve 14 of the main valve 7 is connected to the lower-pressure tank 18 via the pipe lines 16 and 22, and the high-pressure oil in the pilot chest 14c is exhausted at a point of time d1 in the timing chart (d) in FIG. 11. When the high-pressure oil in the pilot chest 14c is exhausted, the valve bodies 13b and 14b move rightward in FIG. 10. Thereby, the exhaust valve 14 of the main valve 7 opens the pipe line 17 which is connected to the lower-pressure tank 18, and closes the feed valve 13 at a point of time e1 in the timing chart (e) of FIG. 11.
Thereby, the high-pressure oil in the second pressure chest 5b of the cylinder 5 is exhausted to the lower pressure tank 18 through the valve chest 7a and the pipe line 17 at a point of time f1 in the timing chart (f) in FIG. 11. When the pressure of the oil in the second pressure chest 5b of the cylinder 5 is reduced, a thrust is generated in downward direction in FIG. 10, and the differential piston 3 starts to move in a direction to open the contact 1 of the circuit breaker at a point of time g1 in the timing chart (g) in FIG. 11. The oil in the circular groove 73 has been exhausted with pushing up the dashpot ring 74. The high pressure oil which is continuously supplied from the accumulator 9 through the restrictor 75 and the pipe line 76 is also exhausted to the lower pressure tank 18 at a point of time i1 in the timing chart (i) in FIG. 11. Even when the opening signal is shutoff at a point of time a3 in the timing chart (a) in FIG. 11 and after that the opening valve 28 is closed, the amplifier valve 8 and the main valve 7 are not returned to the initial positions since the high-pressure oil in the pipe line 77 is exhausted when the amplifier valve 8 and the main valve 7 are once switched.
At this time, a high-pressure oil is supplied to the closing operation control device 61 from the accumulator 9 through the pipe line 59 and the restrictor 54. Thereby, the piston 62 always pushes on the back of the latch 63. When the opening operation of the contact 1 by the differential piston 3 is completed, the pin 50 provided on the differential piston 3 has passed the latch 63 (at a point of time g2 in the timing chart (g) in FIG. 11), and the latch 63 starts to rotate in counterclockwise direction in FIG. 10 around the pivot 64 (at a point of time h1 in the timing chart (h) in FIG. 11). Thereby, the latch 63 engages with the pin 50 (at a point of time h2 in the timing chart (h) in FIG. 11).
In a condition that the opening operation of the contact 1 is completed, a bottom face 74a of the dashpot ring 74 contacts a face 5c of the cylinder 5, tightly. As a result, the high-pressure oil from the accumulator 9 is supplied to the circular groove 73 and the pipe lines 76 and 77 through the restrictor 75 (at a point of time 12 in the timing chart (1) in FIG. 11). Furthermore, the high-pressure oil is continuously supplied to the pilot chest 19c through the restrictor 72 and the pipe line 71 (at a point of time b2 in the timing chart (b) in FIG. 11). When the pressure of the oil in the pilot chest 19c reaches a predetermined value, a back-pressure, which is applied to the supplemental feed valve 20 which is on a closed state overcomes the back-pressure applied to the supplemental exhaust valve 19. Therefore, the supplemental exhaust valve 19 and the supplemental feed valve 20 start to move in one body (at a point of time c2 in the timing chart (c) in FIG. 11). The supplemental exhaust valve 19 of the amplifier valve 8 closes the pipe line 22 communicating to the lower-pressure tank 18 and opens the supplemental feed valve 20. As a result, the high-pressure oil reaches the pilot chest 14c of the exhaust valve 14 through the pipe lines 12, 51 and 16. And the high-pressure oil in he pilot chest 14c switches the main valve 7, again. When the exhaust valve 14 receives the high-pressure oil in the pilot chest 14c, it closes the pipe line 17 communicating to the lower-pressure tank 18 and opens the feed valve 13 at a point of time e2 in the timing chart (e) in FIG. 11.
As a result, the high-pressure oil reaches the second pressure chest 5b of the cylinder 5 through the feed valve 13 and the pipe line 11. A thrust in upward direction in FIG. 10 is generated due to the difference between the areas of the larger piston area side and the smaller piston area side of the differential piston 3 which respectively receive the pressure at a point of time f2 in the timing chart (f) in FIG. 11. However, the latch 63 has already been engaged with the pin 50 (at the point of time h2 in the timing chart (h) in FIG. 11), and a back-pressure due to the high-pressure oil which is supplied through the restrictor 54 and the pipe line 59 is applied to the piston 62, so that the thrust in the upward direction is received by the latch 63 and the opened state of the contact of the circuit breaker shown in FIG. 12 is maintained.
Next, the closing operation of the contact 1 is described below. In FIG. 12, when a closing signal is inputted to the closing electro-magnetic device 35 for closing the main contact 1, the moving core 35a is driven and the driving force is applied to the closing valve 38 via the operation rod 33, and the ball-shaped valve body 29 is opened. Therefore, the pipe lines 56 and 59 are connected to the lower-pressure tank 18, and the high-pressure oil therein is exhausted to the lower-pressure tank 18. As a result, the force for pushing the latch 63 by the piston 62 is removed. As mentioned above, since the shape of the latch 63 is formed in a manner to release the engagement with the pin automatically by the thrust of the differential piston 3 when the pressure by the piston 62 is removed, the differential piston 3 starts to move upward and finally completes the closing operation of the main contact 1. On the other hand, the high-pressure oil in the accumulator 9 is gradually supplied to the pipe line 59 through the pipe line 52 and the restrictor 54. When the differential piston 3 completes the closing operation, the high-pressure oil is filled in the pipe line 59 for standing the next opening operation of the main contact, as shown in FIG. 10.
The first conventional hydraulic operation apparatus 4 shown in FIG. 9 is configured above, and the second hydraulic operation apparatus 104 is configured substantially the same.
In a circuit breaker with resistor contact, the main contact is opened first and the resistor contact must be opened shortly before the final step of the opening operation of the main contact. As a method for opening the main contact and the resistor contact serially, it is general to input the opening signal to the opening electro-magnetic device 36 of the first hydraulic operation apparatus 4 for opening the main contact, at first. After counting a predetermined time period by using a time rug relay and the like, an excitation signal corresponding to the opening signal is inputted to the opening electromagnetic device 36 of the second hydraulic operation apparatus 104 for opening the resistor contact.
When the time periods which are necessary for driving the opening electro-magnetic devices of respective hydraulic operation apparatuses are different, the resister contacts are also closed at different timings in opening operation of the circuit breaker. Thereby, the over voltage during the opening operation can not be restrained sufficiently. Furthermore, when the time period during the while the resistor contact is kept connected becomes longer, a severe heat duty is demanded to the resisters. Let us suppose such an accident occurs that the opening signal can not input to the hydraulic operation apparatuses owing to the disconnection of the control circuit which is to output an excitation signal to the electro-magnetic devices corresponding to the opening command to the hydraulic operation apparatuses. In such a case, only the main contact or the resistor contact is opened and the other is not opened. Therefore, the main contact and the resistor contacts can not be opened serially.